Process of coloring leather.



PATBNTED APR. s.,` 19o?.

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APPLICATION FILED JULY 9. 1906v Z/MWZ@ ca., wAsmNaroN. n. c.

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WILLIAM M. N ORRIS, OF PRINCETON, NEW JERSEY.

' PROCESS OF COLOFHNG LEATHER.

Specification of Letters Patent.

Patented April 30, 1907.

Application tiled July 9. 1906. Serial No. 325,245.

To a/ZZ .wh/0m, it nto/y concern.-

Be it known that I, WILLIAM M. Nonnrs, a citizen of the United States, residing at Princeton, in the county of Mercer, State of New Jersey, have invented a new and useful Method of Coloring Leather, of which the following is a specication.

My invention consists of certain improvements in a method of coloring or dyeing I- leather, whereby I can with economy obtain deep, rich and more permanent shades'of black, and attain other advantages which are duly set forth hereinafter.

y though my process or method is applicable to coloring or dyeing hides and skins of all descriptions, I will describe the method as applicable to chrome-tanned goat skins. @ther leathers may be colored or dyed in the same manner with such changes in the quantity of materials employed and manipulations as their different sizes and characters would require.

In the drawing, I have shown a perspective view of one form of apparatus for carrying out the method or process, but make no claim thereto nor is the present invention restricted to the employment of such form of apparatus.

I employ a drum 1, a form of which, suitable .for my purpose, is shown in the accompanying drawings, and place therein say four hundred and fifty pounds of skins as they come from the shaving machines, and thirty gallons of warm water. The covering head 2 of the drum is then closed. N ow dissolve two and one-half pounds of permanganate of potash in forty-five gallons of warm water and then add two and one-half pounds of muriatic acid 21o Baume, this solution being inserted in the drum through the opening 3 in the gudgeon thereof. After ten minutes, stop rotation of the drum, then open the same and allow the liquor which is now spent to'run oil". Again replace the head of the drum, allow the latter tov rotate and add as before through the gudgeon, two gallons of iron liquor" which has been previously mixed with forty-five gallons of warm water. After ten minutes, stop the rotation of the drum, open the same and allow the liquor', which is now spent, to run oil. Next dissolve in forty-five gallons of warm water, three pounds of extract of logwood, or other suitable vegetable extract, and three pounds of sal soda (carbonate of soda), and after the drum has been closed and allowed to rotate as before, add the saine through the gudgeon. After ten minutes, stop the drum, open the head and remove the skins. The coloring process is now complete and the stock is washed thoroughly .in a twister7 with warm water for fifteen or twenty ininutes before being stained, fat liquored and finished in any suitablemanner, either for glazed or dull stock.

The iron liquor7 referred to above may be prepared by dissolving scrap iron in dilute connncrcial acetic acid and the solution prepared ready for use should stand l0@ on a Baume hydrometer. But any suitable ferrous salt of iron maybe used.

The other materials mentioned, permanganate of potash, niuriatic acid, sal soda and logwood extract are well known articles' of commerce.

The temperature of the warm waterH referred to above should be in all cases about 110O Fall. in summer and from 12()O to 1250 F ah. in winter.

Ilydrochloric acid. must never be added to a hot concentrated solution of permanganate of potash, as this would result in the evolution of chlorin and the formation of manganous chlorid which is not the salt of manganese desired.

The Jmuriatic acid is added to the permanganate solution when all the required amount of water is present.

As an acidulated solution of permanganate of potash strikes very quickly on leather, there must be a sul'licient amount of water present in the drum in order to secure an even distribution over the stock.

Skins which have not been washed clean from the hypo-bath should have the requisite amount of acid added to the first thirty gallons of water referred to. lhe pei-manganate dissolved in water is added after an interval of about five minutes.

To determine whether a sufficient amount of permanganate has been used, throw a skin over a horse exposed to the sunlight and observe after an interval of fifteen or twenty minutes, whether or not the brown color is uniform and even. If light streaks or spots develop, it indicates that the sulfurous acid in the stock is not entirely neutralized or killed. Such stock should have more permanganate, but it must always be borne in mind that permanganate of potash is a powerful oxidizing agent and can only be safely employed in very dilute solutions.

IIO

` (never alkaline).

"EST VIL On bark and vegetable tanned leather, weaker solutions of permanganate than those prescribed above should be employed. lll/Then chrome-tanned skins are treated to an asidulated solution of permaganate of potash, all of the latter quickly combines with the stock7 imparting to it a brown color. .lt is reduced by the stock itself to some extent and it thoroughly destroys any sulfurous acid present which has been carried over from the l hypo bath. Now following this with a ferrous salt of iron, all the remaining p ermanganate compound is reduced to an insoluble modification and the ferrousiron is oxidized to a ferric state and is at once absorbed by the stock. The final treatment with logwood and soda forms a perfectly insoluble and permanent jet-black which will last as long as the leather itself.

The function of the soda is not merely to assist in the formation of the color-lake by neutralizing' the acid liberated rom the iron liquor7 but it is necessary to have sufficient alkali present to neutralize all of the acid in the stock which has been taken up from previous steps of the process as well as any acid carried over from the hypo-bath. Stock should be neutral., or only very slightly acid, After this treatment, it can then be washed perfectly clean in a short time.

The stock being placed in a drum and not removed until all the coloring operations are completed, saves much handling and labor.

Only very small quantities of the various chemicals used are required for a large number of skins, not only making the process a very economical one effecting a considerable saving over present methods,but thus securing the softest possible method of applying coloring materials as the grain 1s neverin the least roughened or contracted.

rlhe stock being thoroughly washed and cleaned before staining and fat liquoring and all sulfurous acid being eliminated, there is no chance for skins colored by this method, showing any bloom or spew when finished.

The remarkable Yline smooth silky feel which permanganate imparts to skins is retained and emphasized by the subsequent treatments.

Skins colored by this process will glaze much brighter and have a far superior finish, more permanent and lasting than when colored by any other method.

In working this process, I have found that the best results were obtained by using the quantities of the materials and the manipulations specified, but l do not confine myself j either' to these proportions or to these methods of manipulation, as considerable modifij cations can be made without departing from j the essential features of my process.

l l l Having thus described my invention, what l claim as new and desire to secure by Letters Patent, is:

l. A step in the process of dyeing leather which consists in subjecting it to an acidulated solution ofpermanganate of potash.

2. A step in the process of dyeing leather which consists in subjecting it to an acidulated solution of permanganate of potash and then to a solution of ferrous salt of iron.

3. Those steps in the process of dyeing leather' which consistsin subjecting it to an acidulated solution of permanganate of potl ash and then to a solution of a ferrous salt of iron and then to a solution of a suitable vegetable extract.

4. rihose steps in the process of dyeing j leather which consists in subjecting it to an acidulated solution of permanganate of potj ash and then to a solution of a ferrous salt of j iron and then to a solution of vegetable eX- l tract and sal soda and then to a'thorough l washing with warm water. l

VILLIAM M. NORRS.

itnesses:

JOHN A. NIEDERSHEIM S. R. CARR. 

